The invention relates generally to automatic test equipment and more particularly a switching DC-DC converter with noise suppression circuitry for use with a semiconductor tester power supply to provide precise voltage and current levels to a high-speed semiconductor device-under-test (DUT).
Semiconductor device manufacturing typically includes test processes at both the wafer and packaged-device levels. The testing is normally carried out by automatic test equipment ATE that simulates a variety of operating conditions to verify the functionality of each device. As is well known in the art, semiconductor devices generally require a source of power in order to function.
As the speeds of modern semiconductors increase, the dynamic current requirements necessary to operate the devices also increase. This is due to many variables, such as the reduction in logic level voltages, higher switching speeds, higher transistor counts, transistor technology, etc. As it stands, modem microprocessors may draw from a few hundred milli-amps in static conditions, to over two-hundred amps during dynamic conditions over the course of a few nanoseconds.
Unlike power supplies that are typically employed in, for example, a personal computer, power supplies for automatic test equipment applications generally must be accurate, fast, and programmable. Device manufacturers often test a semiconductor part to characterize extreme operating ranges, and desire high accuracy to enable proper xe2x80x9cbinningxe2x80x9d of the highest speed devices. Just a few millivolts of inaccuracy can result in a gigahertz speed device sorted in a lower speed bin. Because higher speed devices command significantly higher prices for manufacturers, power supply accuracy plays an important role in the overall test process.
Conventional DUT power supplies typically include a switching DC-DC converter to step-down a high voltage to a lower DUT operating voltage. It is well-known in the art that switching DC-DC converters provide a more efficient conversion scheme in terms of power dissipation than, for example, linear conversion schemes. A typical switching converter includes switching circuitry for producing a square-wave signal from the high-voltage DC, and conversion circuitry in the form of a transformer coupled with a diode and relatively large inductor/capacitor components for converting the square-wave signal into the low voltage DC level.
While the conventional switching converter scheme described above works well for its intended applications to power relatively slower-speed and low-power consuming semiconductor devices, for high-speed device applications the design is susceptible to noise problems. As logic voltage levels decrease, noise in the form of ringing as the circuit switches undesirably affects the DC output supplied to the semiconductor device. Moreover, the large capacitors that are commonly employed in conventional schemes tend to generate large amounts of noise. For important high-accuracy applications such as in the field of automatic testing, ringing and other forms of noise may cause improper fail data in the test results because of inaccuracy in the DUT supply voltage. This would possibly lower the device manufacturing yields.
What is needed and heretofore unavailable is a high accuracy switching DC-DC converter that is adaptable for use in a DUT power supply and that can minimize noise and power dissipation. The switching DC-DC converter of the present invention satisfies these needs.
The switching DC-DC converter of the present invention provides high-speed voltage conversion performance to devices-under-test while maintaining stringent accuracy requirements. As a result, semiconductor device manufacturers can maximize device yields and correspondingly reduce test costs.
To realize the foregoing advantages, the invention in one form comprises a switching DC-DC converter unit is disclosed that includes an input for receiving a first DC voltage from a DC power source and switching circuitry coupled to the input to generate a switched alternating voltage from the first DC voltage. The switching circuitry includes a plurality of semiconductor switches having respective gate, source and drain leads, and further including noise suppression elements disposed on the drain leads. The unit further includes transformer circuitry coupled to the output of the switching circuitry and conversion circuitry disposed at the output of the transformer circuitry to convert the switched alternating voltage to a second DC voltage.
In another form, the invention comprises a switching DC-DC converter system including a plurality of switching converter units disposed in parallel. Each of the converter units includes a first input for receiving a first DC voltage from a DC power source and switching circuitry coupled to the input to generate a stepped voltage waveform from the constant input voltage. A phase controller sequentially switches the converter units according to predetermined timings to generate a multi-phased output voltage waveform while conversion circuitry converts the switched alternating output voltage to a second DC voltage.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.